diff --git a/src/g_hexen/a_korax.cpp b/src/g_hexen/a_korax.cpp
index 2597fe8cd..7f0d3a43c 100644
--- a/src/g_hexen/a_korax.cpp
+++ b/src/g_hexen/a_korax.cpp
@@ -484,7 +484,7 @@ AActor *P_SpawnKoraxMissile (const DVector3 &pos, AActor *source, AActor *dest,
 	DAngle an;
 	double dist;
 
-	th = Spawn (type, source->PosPlusZ(-source->Floorclip), ALLOW_REPLACE);
+	th = Spawn (type, pos, ALLOW_REPLACE);
 	th->target = source; // Originator
 	an = th->AngleTo(dest);
 	if (dest->flags & MF_SHADOW)
diff --git a/src/p_spec.cpp b/src/p_spec.cpp
index a3d0858ee..e4138afd8 100644
--- a/src/p_spec.cpp
+++ b/src/p_spec.cpp
@@ -983,6 +983,13 @@ void P_SpawnPortal(line_t *line, int sectortag, int plane, int bytealpha, int li
 
 			AStackPoint *anchor = Spawn<AStackPoint>(pos1, NO_REPLACE);
 			AStackPoint *reference = Spawn<AStackPoint>(pos2, NO_REPLACE);
+
+			// In some situations it can happen that the sector here is not the frontsector of the anchor linedef,
+			// because some colinear node line with opposite direction causes this to be positioned on the wrong side.
+			// Fortunately these things will never move so it should be sufficient to set the intended sector directly.
+			anchor->Sector = line->frontsector;
+			reference->Sector = lines[i].frontsector;
+
 			reference->special1 = linked ? SKYBOX_LINKEDPORTAL : SKYBOX_PORTAL;
 			anchor->special1 = SKYBOX_ANCHOR;
 			// store the portal displacement in the unused scaleX/Y members of the portal reference actor.
diff --git a/src/r_bsp.cpp b/src/r_bsp.cpp
index 014f8be06..de083d7b0 100644
--- a/src/r_bsp.cpp
+++ b/src/r_bsp.cpp
@@ -513,6 +513,23 @@ sector_t *R_FakeFlat(sector_t *sec, sector_t *tempsec,
 }
 
 
+bool R_SkyboxCompare(sector_t *frontsector, sector_t *backsector)
+{
+	AActor *frontc = frontsector->SkyBoxes[sector_t::ceiling];
+	AActor *frontf = frontsector->SkyBoxes[sector_t::floor];
+	AActor *backc = backsector->SkyBoxes[sector_t::ceiling];
+	AActor *backf = backsector->SkyBoxes[sector_t::floor];
+
+	// return true if any of the planes has a linedef-based portal (unless both sides have the same one.
+	// Ideally this should also check thing based portals but the omission of this check had been abused to hell and back for those.
+	// (Note: This may require a compatibility option if some maps ran into this for line based portals as well.)
+	if (frontc != NULL && (frontc->special1 == SKYBOX_PORTAL || frontc->special1 == SKYBOX_LINKEDPORTAL)) return (frontc != backc);
+	if (frontf != NULL && (frontf->special1 == SKYBOX_PORTAL || frontf->special1 == SKYBOX_LINKEDPORTAL)) return (frontf != backf);
+	if (backc != NULL && (backc->special1 == SKYBOX_PORTAL || backc->special1 == SKYBOX_LINKEDPORTAL)) return true;
+	if (backf != NULL && (backf->special1 == SKYBOX_PORTAL || backf->special1 == SKYBOX_LINKEDPORTAL)) return true;
+	return false;
+}
+
 //
 // R_AddLine
 // Clips the given segment
@@ -655,6 +672,10 @@ void R_AddLine (seg_t *line)
 		// Window.
 			solid = false;
 		}
+		else if (R_SkyboxCompare(frontsector, backsector))
+		{
+			solid = false;
+		}
 		else if (backsector->lightlevel != frontsector->lightlevel
 			|| backsector->GetTexture(sector_t::floor) != frontsector->GetTexture(sector_t::floor)
 			|| backsector->GetTexture(sector_t::ceiling) != frontsector->GetTexture(sector_t::ceiling)
diff --git a/src/textures/pngtexture.cpp b/src/textures/pngtexture.cpp
index ac369a135..e47fa62c0 100644
--- a/src/textures/pngtexture.cpp
+++ b/src/textures/pngtexture.cpp
@@ -659,6 +659,10 @@ int FPNGTexture::CopyTrueColorPixels(FBitmap *bmp, int x, int y, int rotate, FCo
 						transpal = true;
 				}
 			}
+			else
+			{
+				lump->Seek(len, SEEK_CUR);
+			}
 			break;
 		}
 		lump->Seek(4, SEEK_CUR);		// Skip CRC
@@ -697,6 +701,7 @@ int FPNGTexture::CopyTrueColorPixels(FBitmap *bmp, int x, int y, int rotate, FCo
 		{
 			bmp->CopyPixelDataRGB(x, y, Pixels, Width, Height, 3, pixwidth, rotate, CF_RGBT, inf,
 				NonPaletteTrans[0], NonPaletteTrans[1], NonPaletteTrans[2]);
+			transpal = true;
 		}
 		break;
 
diff --git a/src/thingdef/thingdef_codeptr.cpp b/src/thingdef/thingdef_codeptr.cpp
index 53685c43b..03f011b41 100644
--- a/src/thingdef/thingdef_codeptr.cpp
+++ b/src/thingdef/thingdef_codeptr.cpp
@@ -3120,7 +3120,7 @@ static bool DoCheckSightOrRange(AActor *self, AActor *camera, double range, bool
 		dz = 0;
 	}
 	double distance = DVector3(pos, twodi? 0. : dz).LengthSquared();
-	if (distance <= range*range)
+	if (distance <= range)
 	{
 		// Within range
 		return true;